1,720,959 research outputs found
Local photolysis using tapered quartz fibres
No full textWe describe a versatile, low-cost photolysis system in which sub-millisecond flashes generated by a xenon flash lamp are conveyed through a silica fibre directly onto a cell. The fibre, which is tapered to a sub-micrometre diameter and sputtered with chromium and aluminium, illuminates an area of about 1 mum(2). Site and timing of photolysis can be chosen independently from other experimental parameters. As an application example we show the spatially heterogeneous distribution of Ca2+-dependent Cl- channels in olfactory receptor neurons
Electrorheological fluids as an electrically controllable acoustic medium: I. Experimental arrangement and application to an absorber of underwater sound
No full textElectrorheological fluids (ERF) change their viscoelastic properties in a strong electric field. A new realm of ERF applications could be underwater acoustics where the construction of absorbers with electrically adjustable properties appears possible. An improved impedance tube has been developed for the measurement of the acoustic properties of ERF and hydroacoustic sound absorbers, employing the so-called two-microphone method. Using the new impedance tube, sound velocity and attenuation of ERFs have been measured as functions of frequency, field strength, and temperature. Further, a laboratory model of an absorber for underwater sound, based on the principle of particle velocity transformation with ERF as viscous fluid, has been built and tested. Within certain limits, the absorber impedance can be controlled by changing the electric field strength applied to the ERF
Electrorheological fluids as an electrically controllable acoustic medium: I. Experimental arrangement and application to an absorber of underwater sound
No full textElectrorheological fluids (ERF) change their viscoelastic properties in a strong electric field. A new realm of ERF applications could be underwater acoustics where the construction of absorbers with electrically adjustable properties appears possible. An improved impedance tube has been developed for the measurement of the acoustic properties of ERF and hydroacoustic sound absorbers, employing the so-called two-microphone method. Using the new impedance tube, sound velocity and attenuation of ERFs have been measured as functions of frequency, field strength, and temperature. Further, a laboratory model of an absorber for underwater sound, based on the principle of particle velocity transformation with ERF as viscous fluid, has been built and tested. Within certain limits, the absorber impedance can be controlled by changing the electric field strength applied to the ERF
Cultural characteristics and in vitro antagonistic activity of two isolates of Mortierella alpina Peyronel
No full textThe aim of the present study was to describe cultural characteristics of two isolates of the zygomycete Mortierella alpina Peyronel, to study the behaviour of these isolates in dual cultures with phytopathogenic fungi, and to investigate mechanisms possibly contributing to the in vitro antagonistic properties of M. alpina. Isolates "BBA 69688" and "29" showed some growth at 5 degreesC, had a maximum growth rate around 25-30 degreesC and did not grow at 37 degreesC. On the nutrient rich media malt extract agar (MEA) and potato dextrose agar (PDA), the isolates produced a dense mycelium, but hyphal growth was most rapid on V8-agar and Czapek-agar (CZA), Sporulation was only observed an soil extract agar (SEA) and the minimal medium SNA. In dual cultures on MEA, both isolates inhibited the growth of various phytopathogenic fungi and lyzed hyphal tips. I.ysis of hyphal tips was not observed on CZA. On MEA, both isolates released endo-cellulase, endo-chitinase, beta-1, 3-glucanase and protease activity into the medium. These enzymes were also produced in shake cultures in malt extract broth (MEB) and potato dextrose broth (PDB). Of the enzyme activities assayed, protease activity appeared to be highest, built on solid media and in shake cultures. On MEA plates, on which M. alpina isolate 69688 had been previously cultured on cellophane sheets, growth of P. ultimum, R. solani and T culmorum was inhibited. However, growth of these fungi was also inhibited, and hyphal tips were lyzed, on precolonized MEA from which the enzymatic activity had been removed by heat treatment. The inhibitory activity of culture filtrate of isolate 29 was reduced following extraction with ethyl acetate. In conclusion, the in vitro antagonistic properties of M. alpina appear to be based on different mechanisms. Production of ethyl-acetate extractable and not extractable metabolites seem to be major factors, whereas the release of lytic enzymes is unlikely to play a role
Cultural characteristics and in vitro antagonistic activity of two isolates of Mortierella alpina Peyronel
No full textThe aim of the present study was to describe cultural characteristics of two isolates of the zygomycete Mortierella alpina Peyronel, to study the behaviour of these isolates in dual cultures with phytopathogenic fungi, and to investigate mechanisms possibly contributing to the in vitro antagonistic properties of M. alpina. Isolates "BBA 69688" and "29" showed some growth at 5 degreesC, had a maximum growth rate around 25-30 degreesC and did not grow at 37 degreesC. On the nutrient rich media malt extract agar (MEA) and potato dextrose agar (PDA), the isolates produced a dense mycelium, but hyphal growth was most rapid on V8-agar and Czapek-agar (CZA), Sporulation was only observed an soil extract agar (SEA) and the minimal medium SNA. In dual cultures on MEA, both isolates inhibited the growth of various phytopathogenic fungi and lyzed hyphal tips. I.ysis of hyphal tips was not observed on CZA. On MEA, both isolates released endo-cellulase, endo-chitinase, beta-1, 3-glucanase and protease activity into the medium. These enzymes were also produced in shake cultures in malt extract broth (MEB) and potato dextrose broth (PDB). Of the enzyme activities assayed, protease activity appeared to be highest, built on solid media and in shake cultures. On MEA plates, on which M. alpina isolate 69688 had been previously cultured on cellophane sheets, growth of P. ultimum, R. solani and T culmorum was inhibited. However, growth of these fungi was also inhibited, and hyphal tips were lyzed, on precolonized MEA from which the enzymatic activity had been removed by heat treatment. The inhibitory activity of culture filtrate of isolate 29 was reduced following extraction with ethyl acetate. In conclusion, the in vitro antagonistic properties of M. alpina appear to be based on different mechanisms. Production of ethyl-acetate extractable and not extractable metabolites seem to be major factors, whereas the release of lytic enzymes is unlikely to play a role
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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